Gimbal system angle compensation

Abstract

Gimbal system angle compensation methods and systems are provided. A particular method includes pointing an antenna at a first target using an initial set of at least four gimbal angles and determining first bore sight pointing errors resulting from a pointing direction of the antenna relative to the first target. The method also includes estimating values of a plurality of independently observable error variables based on the first bore sight pointing errors. The method further includes determining a set of gimbal angle corrections based on the values of the plurality of independently observable error variables.

1. A method, comprising:
 determining a set of at least four nominal gimbal angles to point an antenna at a target based at least partially on location information associated with the target; 
 identifying a set of corrected gimbal angles based on the set of at least four nominal gimbal angles and based on a set of gimbal angle corrections, wherein the set of gimbal angle corrections are determined based at least partially on one or more bore sight measurements of the antenna; and 
 pointing the antenna using the set of corrected gimbal angles. 
 
   
   
     2. The method of  claim 1 , wherein determining the set of gimbal angle corrections based at least partially on one or more bore sight measurements of the antenna comprises:
 determining values of a plurality of independently observable error variables based on the one or more bore sight measurements, and 
 determining the set of gimbal angle corrections by applying the values of the independently observable error variables to a mapping matrix. 
 
   
   
     3. A system comprising:
 a host vehicle interface adapted to be coupled to a host vehicle; and 
 a gimbal system, comprising:
 a first gimbal coupled to the host vehicle interface; 
 a platform coupled to the first gimbal; 
 a second gimbal coupled to the platform; and 
 a first directional payload interface coupled to the second gimbal; 
 
 wherein an attitude of a first directional payload coupled to the first directional payload interface is adjustable using the gimbal system based on gimbal angle compensation logic. 
 
   
   
     4. The system of  claim 3 , further comprising a controller including the gimbal angle compensation logic, wherein the controller determines gimbal angle error values based on a calibration of the gimbal system to a bore sight of the first directional payload. 
   
   
     5. The system of  claim 3 , further comprising a beacon tracking module to determine gimbal angle error values, either directly obtained or derived from bore sight pointing errors, used by the gimbal angle compensation logic by changing gimbal angles of the gimbal system to detect a maximum ground beacon signal attained. 
   
   
     6. The system of  claim 3 , further comprising an antenna mapping module to determine gimbal angle error values, either directly obtained or derived from bore sight pointing errors. 
   
   
     7. The system of  claim 3 , wherein the gimbal angle compensation logic is adapted to receive host vehicle attitude data and to adjust the attitude of the first directional payload to maintain a specified pointing direction. 
   
   
     8. The system of  claim 3 , wherein the platform comprises a platform interface and a second directional payload coupled to the platform interface, and wherein an attitude of the second directional payload is adjustable by the gimbal angle compensation logic using the first gimbal. 
   
   
     9. The system of  claim 8 , wherein the gimbal angle compensation logic is adapted to receive host vehicle attitude data, to adjust the attitude of the first directional payload to maintain a first specified pointing direction, and to adjust the attitude of the second directional payload to maintain a second specified pointing direction. 
   
   
     10. A method, comprising:
 pointing an antenna at a first target using an initial set of at least four gimbal angles, wherein coordinates of the first target are known; 
 determining first bore sight pointing errors resulting from a pointing direction of the antenna relative to the first target; 
 estimating values of a plurality of independently observable error variables based on the first bore sight pointing errors; and 
 determining, based on the values of the plurality of independently observable error variables, a set of gimbal angle corrections. 
 
   
   
     11. The method of  claim 10 , wherein the values of the plurality of independently observable error variables are estimated based on the bore sight pointing errors using an estimation algorithm. 
   
   
     12. The method of  claim 10 , further comprising:
 determining an adjusted set of at least four gimbal angles or a subset of the gimbal angles based on the set of gimbal angle corrections; 
 pointing the antenna at the first target using the adjusted set of at least four gimbal angles or the subset of the gimbal angles; 
 determining subsequent bore sight pointing errors resulting from the pointing direction of the antenna using the adjusted set of at least four gimbal angles or the subset of the gimbal angles relative to the first target; 
 estimating the values of the plurality of independently observable error variables based at least partially on the subsequent bore sight pointing errors; and 
 determining, based on the values of the plurality of independently observable error variables, a subsequent set of gimbal angle corrections. 
 
   
   
     13. The method of  claim 12 , wherein a time period between determining the set of gimbal angle corrections and determining the subsequent set of gimbal angle corrections is selected to reduce influences of cyclic errors. 
   
   
     14. The method of  claim 10 , further comprising:
 pointing the antenna at the first target using a second set of at least four gimbal angles, wherein the second set of at least four gimbal angles are different than the initial set of at least four gimbal angles; 
 determining second bore sight pointing errors resulting from the pointing direction of the antenna using the second set of at least four gimbal angles relative to the first target; 
 estimating the values of the plurality of independently observable error variables based on the first bore sight pointing errors and the second bore sight pointing errors; and 
 determining, based on the values of the plurality of independently observable error variables, a subsequent set of gimbal angle corrections for pointing the antenna. 
 
   
   
     15. The method of  claim 10 , further comprising:
 pointing the antenna at a second target using a second set of at least four gimbal angles, wherein coordinates of the second target are known and are different than the coordinates of the first target; 
 determining second bore sight pointing errors resulting from the pointing direction of the antenna using the second set of at least four gimbal angles relative to the second target; 
 estimating the values of the plurality of independently observable error variables based on the first bore sight pointing errors and the second bore sight pointing errors; and 
 determining, based on the values of the plurality of independently observable error variables, a second set of gimbal angle corrections for pointing the antenna. 
 
   
   
     16. The method of  claim 10 , wherein the initial set of at least four gimbal angles are used to position a first gimbal coupled to a host vehicle and a second gimbal coupled to the first gimbal and coupled to the antenna. 
   
   
     17. The method of  claim 10 , further comprising:
 determining the initial set of four gimbal angles based on initial estimates of the values of the plurality of independently observable error variables and information about the coordinates of the first target. 
 
   
   
     18. The method of  claim 10 , wherein:
 the antenna is coupled to an antenna gimbal; 
 the antenna gimbal is coupled to a platform; 
 the platform is coupled to a platform gimbal; 
 the platform gimbal is coupled to a host vehicle; and 
 the initial set of at least four gimbal angles are used to adjust gimbal angles of the platform gimbal and gimbal angles of the antenna gimbal. 
 
   
   
     19. The method of  claim 18 , further comprising determining the initial set of at least four gimbal angles based at least partially on attitude information related to the host vehicle and the coordinates of the first target. 
   
   
     20. The method of  claim 19 , wherein the independently observable error variables include at least one error variable related to one or more of an attitude of the host vehicle, an attitude of the platform, an attitude of the antenna, orthogonality of axes of the antenna gimbal, and orthogonality of axes of the platform gimbal.